Provider presets and factory (#44)

Co-authored-by: dev_agent <dev_agent@cubecraftlabs.com>
Co-committed-by: dev_agent <dev_agent@cubecraftlabs.com>

internal/ai/llm/settings.go

@@ -0,0 +1,68 @@
+package llm
+
+import "errors"
+
+// Settings is the household's AI configuration, the input to
+// presets.FromSettings. The caller fills it from the db.AiSetting row and
+// the service config; this package does not import internal/db.
+//
+//	llm.Settings{
+//		Provider:    row.Provider,
+//		BaseURL:     row.BaseUrl,
+//		Model:       row.Model,
+//		Temperature: row.Temperature,
+//		PublicURL:   cfg.PublicURL.String(), // MEALQUEST_PUBLIC_URL
+//	}
+//
+// Settings never holds the API key: the caller decrypts it and passes it
+// to presets.FromSettings separately.
+type Settings struct {
+	// Provider names the preset: "anthropic", "openai", "openrouter",
+	// "ollama" or "openai_compatible".
+	Provider string
+	// BaseURL is the API root. It is required for ollama and
+	// openai_compatible; the other presets fix their own, and a non-empty
+	// value must equal it.
+	BaseURL string
+	// Model is the model id Generate requests. It is required.
+	Model string
+	// Temperature is the household's sampling temperature. It is sent with
+	// every request that sets none, except to models that reject it.
+	Temperature float64
+	// PublicURL is MEALQUEST_PUBLIC_URL. OpenRouter requires it and
+	// receives it as the HTTP-Referer header; other presets ignore it.
+	PublicURL string
+	// StructuredOutput selects how an OpenAI-compatible preset asks for
+	// JSON: "json_schema", "json_object" or "prompt_only". Empty selects
+	// the preset's default, json_schema. Each preset allows only the modes
+	// it lists; anthropic and ollama allow none, so it must be empty.
+	StructuredOutput string
+}
+
+// Configuration errors from presets.FromSettings. Each is distinct and
+// matches with errors.Is.
+var (
+	// ErrUnknownProvider means Settings.Provider names no preset.
+	ErrUnknownProvider = errors.New("llm: unknown provider")
+	// ErrMissingKey means the preset requires an API key and none was
+	// given.
+	ErrMissingKey = errors.New("llm: API key is required")
+	// ErrUnexpectedKey means an API key was given to a preset that sends
+	// none.
+	ErrUnexpectedKey = errors.New("llm: provider takes no API key")
+	// ErrInvalidKey means the API key is not a valid HTTP header value:
+	// it has a control character such as CR or LF.
+	ErrInvalidKey = errors.New("llm: API key is not a valid header value")
+	// ErrMissingBaseURL means the preset requires a base URL and none was
+	// given.
+	ErrMissingBaseURL = errors.New("llm: base URL is required")
+	// ErrMissingModel means Settings.Model is empty.
+	ErrMissingModel = errors.New("llm: model is required")
+	// ErrMissingPublicURL means the preset requires Settings.PublicURL and
+	// it is empty.
+	ErrMissingPublicURL = errors.New("llm: public URL is required")
+	// ErrInvalidSetting means a setting has a value the preset does not
+	// accept, such as a base URL other than the preset's, an unsupported
+	// structured output mode or a negative temperature.
+	ErrInvalidSetting = errors.New("llm: invalid setting")
+)